1. Field of the Invention
This invention relates to an image forming apparatus for performing development by using a developer in the form of a powder, and relates more particularly to a toner recycling mechanism provided in an image forming apparatus wherein a plurality of image forming means which constitute an image forming section are grouped into a photosensitive member unit and a development unit which units are detachably mounted in the apparatus body.
2. Description of the Prior Art
Recently, for image forming apparatus, e.g., electrophotographic reproducing machine for use in offices, a method of mounting various components is adopted wherein image forming means such as a photosensitive member, a charging device, developing device, a transfer device and a cleaning device are built in a common support frame for unitizing in order to improve the accuracy with which the components are positioned relative to each other and to facilitate maintenance, and the support frame is mounted in the apparatus body.
To form such components of the image forming section into a unit, a type of construction such as one disclosed in Japanese Patent Publication No. 63-10424 is ordinarily adopted in which the developing device is constructed as one unit separately from a unit of other components including a photosensitive member, a charging device, a transfer device and a cleaning device and is independently mounted in or detached from the apparatus body in consideration of the lifetime and the frequency of maintenance. However, the invention of Japanese Patent Publication No. 63-10424 has no mechanism for recycling the toner.
A type of image forming apparatus having toner recycling functions, such as one disclosed in Japanese Utility Model Publication No. 55-18843, is known. In this apparatus, the residual toner remaining on the photosensitive member is collected by the cleaning device after an image has been transferred, and the collected toner is supplied to the development device to be reused as developer. If this type of apparatus is designed to incorporate the cleaning device and the developing device in different units, a toner feeding means for connecting these devices must be detachably connected between the cleaning device and the developing device and must be of a movable type capable of retracting from one of the two units so as to enable the other only to be dismounted.
It is of course necessary to prevent the toner from leaking or spilling at the time of detachment or retracting of such a feeding means. Therefore the structure of a resulting toner recycling mechanism is necessarily complicated, and handling such a mechanism is troublesome.
An image forming apparatus wherein a photosensitive member, a developing device, a cleaning device and a toner recycling mechanism are formed as one unit and detachably mounted on the apparatus body, such as one disclosed in Japanese Patent Laid-Open No. 57-138652, is known.
However, in this invention all components are formed as one body, so that the apparatus becomes large in size and the operations of attaching and detaching become difficult. Further, in case that the photosensitive member is different in lifetime from the developing device, both are replaced at the same time according to the shorter lifetime, even if one of the photosensitive member and the developing device which is longer in lifetime can still be used.